The present invention relates to low compression, resilient golf balls and portions thereof formed the conversion reaction of sufficient amounts of polybutadiene, a free radical source, and a cis-to-trans catalyst to convert a portion of cis-isomer to trans-isomer in the polybutadiene, which reaction occurs at a sufficient temperature to form the material that contains trans-isomer and cis-isomer, wherein said material has an amount of trans-isomer greater than the amount of trans-isomer present before the conversion reaction, at least one intermediate layer disposed about the center and including a resilient polymer component and a reinforcing polymer component present in an amount sufficient to provide an uncrosslinked first mixture having a rigidity as determined by a flexural modulus greater than about 3.5 MPa (508 psi), and a cover being disposed about the core.
Conventional golf balls can be divided into several general classes: (a) solid golf balls having one or more layers, and (b) wound golf balls. Solid golf balls include one-piece balls, which are easy to construct and relatively inexpensive, but have poor playing characteristics and are thus generally limited for use as range balls. Two-piece balls are constructed with a generally solid core and a cover and are generally popular with recreational golfers because they are very durable and provide maximum distance. Balls having a two-piece construction are commonly formed of a polymeric core encased by a cover. Typically, the core is formed from polybutadiene that is chemically crosslinked with zinc diacrylate and/or other similar crosslinking agents. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Solid golf balls also include multi-layer golf balls that are comprised of a solid core of one or more layers and/or a cover of one or more layers. These balls are regarded as having an extended range of playing characteristics.
Wound golf balls are generally preferred by many players due to their high spin and soft xe2x80x9cfeelxe2x80x9d characteristics. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material and a cover. Wound balls generally are more difficult and expensive to manufacture than solid two-piece balls.
A variety of golf balls designed to provide a wide range of playing characteristics, i.e., the compression, velocity, xe2x80x9cfeel,xe2x80x9d and spin, that can be optimized for various playing ability, are known in the prior art. One of the most common polymer components present in modem golf ball construction, in addition to ionomers, is polybutadiene and, more specifically, polybutadiene having a high cis-isomer concentration. The use of a polybutadiene having a high cis-concentration results in a very resilient and rigid golf ball, especially when coupled with a hard cover material. These highly resilient golf balls have a relatively hard xe2x80x9cfeelxe2x80x9d when struck by a club. Soft xe2x80x9cfeelxe2x80x9d golf balls constructed with a high cis-polybutadiene have low resilience. In an effort to provide improved golf balls, various other polybutadiene formulations have been prepared, as discussed below.
U.S. Pat. No. 3,239,228 discloses a solid golf ball having a core molded of polybutadiene rubber with a high sulfur content, and a cover. The polybutadiene content of the core is stereo-controlled to the configuration 25-100 percent cis- and 0-65 percent trans-1,4-polybutadiene, with any remainder having a vinyl configuration of polybutadiene. A preferred embodiment of the polybutadiene golf ball core contains 35 percent cis-, 52 percent trans-, and 13 percent vinyl-polybutadiene. The level of trans- and vinyl-content are disclosed to be unimportant to the overall playing characteristics of the polymer blend.
British Patent No. 1,168,609 discloses a molding composition from which improved golf ball cores can be molded and which contains cis-polybutadiene as a basic polymer component. The core polymer component typically includes at least 60 percent cis-polybutadiene, with the remainder being either the trans- or vinyl-forms of polybutadiene. In a preferred embodiment, the core polybutadiene component contains 90 percent cis-configuration, with the remaining 10 percent being either the trans- or vinyl-configurations of 1,4-polybutadiene.
U.S. Pat. Nos. 3,572,721 and 3,572,722 disclose a solid, one- or two-piece golf ball, with the two-piece ball having a core and a cover. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene which may be present in an amount from at least 90 percent, with the remainder being the cis- and/or vinyl configuration.
British Patent No. 1,209,032 discloses a two- or three-piece golf ball having a core and a cover. The core or cover material can be any material capable of being crosslinked. In particular, the material can be a polymer or a copolymer of butadiene or isoprene. Preferably, the polymer component is polybutadiene having a cis content of greater than 50 percent by weight.
U.S. Pat. No. 3,992,014 discloses a one-piece, solid golf ball. The golf ball material is typically polybutadiene, with a stereo-configuration selected to be at least 60 percent cis-polybutadiene, with the remaining 40 percent being the trans-polybutadiene and/or 1,2-polybutadiene (vinyl) isomers.
U.S. Pat. No. 4,692,497 discloses a golf ball and material thereof formed by curing a diene polymer including polybutadiene and a metal salt of an alpha, beta ethylenically unsaturated acid using at least two free radical initiators.
U.S. Pat. No. 4,971,329 discloses a solid golfball made from a polybutadiene admixture of cis-1,4 polybutadiene and 1,2 polybutadiene, a metal salt of an unsaturated carboxylic acid, an inorganic filler, and a free radical initiator. The admixture has about 99.5 percent to about 95 percent by weight of cis-1,4 polybutadiene and about 0.5 percent to about 5 percent by weight of 1,2 polybutadiene.
U.S. Pat. No. 5,252,652 discloses a one-piece or multi-layered golf ball core with improved flying performance from a rubber composition comprising a base rubber, preferably 1,4-polybutadiene with a cis-content of at least 40 mole percent, an unsaturated carboxylic acid metal salt, an organic peroxide, and an organic sulfur compound and/or a metal salt thereof. The organic sulfur compound and/or a metal salt is typically present in an amount from about 0.05 to 2 parts per hundred by weight and the organic peroxide is typically present in an amount from about 0.5 to 3 parts per hundred by weight of the total polymer component.
European Patent No. 0 577 058 discloses a golf ball containing a core and a cover that is formed as two separate layers. The inner layer of the cover is molded over the core and is formed from ionomer resin. The outer layer of the cover is molded over the inner layer and is formed from a blend of natural or synthetic balata and a crosslinkable elastomer, such as polybutadiene. In one embodiment of the outer layer of the cover, the elastomer is 1,4-polybutadiene having a cis-structure of at least 40 percent, with the remaining 60 percent being the trans-polybutadiene isomer. A preferred embodiment contains a cis-structure of at least 90 percent and more preferably, a cis-structure of at least 95 percent.
U.S. Pat. No. 5,697,856 discloses a solid golf ball having a core and a cover wherein the core is produced by vulcanizing a base rubber composition containing a butadicne rubber having a cis-polybutadiene structure content of not less than 90 percent before vulcanization. The amount of trans-polybutadiene structure present after vulcanization is 10 to 30 percent, as amounts over 30 percent are alleged to detrimentally result in cores that are too soft with deteriorated resilience performance, and to cause a decrease in golf ball performance. The core includes a vulcanizing agent, a filler, an organic peroxide, and an organosulfur compound.
British Patent No. 2,321,021 discloses a solid golf ball having a core and a cover formed on the core and having a two-layered cover construction having an inner cover layer and an outer cover layer. The outer cover layer is comprised of a rubber composite that contains 0.05 to 5 parts by weight of an organic sulfide compound. The core rubber composition comprises a base rubber, preferably 1,4-polybutadiene having a cis-content of at least 40 percent by weight, a crosslinking agent, a co-crosslinking agent, an organic sulfide, and a filler. The crosslinking agent is typically an organic peroxide present in an amount from 0.3 to 5.0 parts by weight and the co-crosslinking agent is typically a metal salt of an unsaturated fatty acid present in an amount from 10 to 40 parts by weight. The organic sulfide compound is typically present from 0.05 to 5 parts by weight.
U.S. Pat. No. 5,816,944 discloses a solid golf ball having a core and a cover wherein the core has a JIS-C hardness of 50 to 80 and the cover has a Shore-D hardness of 50 to 60. The core material includes vulcanized rubber, such as cis-polybutadiene, with a crosslinker, an organic peroxide, an organosulfur compound and/or a metal-containing organosulfur compound, and a filler.
U.S. Pat. No. 6,039,910 discloses a golf ball core and method of allegedly reducing the eccentricity of an inner layer to an outer layer by penetrating the inner layer into a part of a seam portion of the outer layer. An unvulcanized material is semivulcanized or vulcanized to form an outer layer half shell whose configuration is generally hemispherical.
Additionally, conventional polymers that have a high percentage of the trans-isomer polybutadiene conformation, such as DIENE 35NF, from Firestone Corp., that has 40 percent cis-isomer and 50 percent trans-isomer polybutadiene, and mixtures of high-cis- and high-trans-isomer content polybutadienes, such as CARIFLEX BR1220, from Shell Corporation, and FUREN 88, from Asahi Chemical Co., respectively, typically do not yield high resilience values and therefore are not desirable.
Manufacturers of quality multi-layer golf balls implement rigorous controls to minimize eccetricity between layers of the balls. When multi-layer golf balls have eccentric layers, the balls tend to spin erratically and flight characteristics are erratic and undesirable.
It is thus desired to prepare golf balls having centers with lower compression, i.e., a softer ball, while having the same or higher resilience than conventional enters. It is alternatively desired to obtain the same or lower compression while achieving greater resilience. Furthermore, it is desired to provide a multi-layer golf ball with substantially concentric layers.
All of the embodiments according to the invention below may be used in any golf ball. Particularly, each embodiment may be used in one of the following embodiments. In one embodiment, the golf ball includes a core and a cover disposed concentrically about the core and the reaction product, also referred to as the material formed from a conversion reaction, is preferably disposed in at least a portion of the core. In a preferred embodiment, the golf ball includes a core having a center and at least one intermediate layer; and a cover disposed concentrically about the core, wherein the reaction product is preferably disposed in the center.
The invention relates to a golf ball having: (1) a center including a reaction product material formed from the conversion reaction of sufficient amounts of polybutadiene, a free radical source, and a cis-to-trans catalyst to convert a portion of cis-isomer to trans-isomer in the polybutadiene, which reaction occurs at a sufficient temperature to form the material that contains trans-isomer and cis-isomer, wherein said material has an amount of trains-isomer greater than the amount of trans-isomer present before the conversion reaction, (2) at least one intermediate layer disposed about the center and including a resilient polymer component and a reinforcing polymer component present in an amount sufficient to provide an uncrosslinked first mixture having a rigidity as determined by a flexural modulus greater than about 3.5 MPa, wherein the center and each intermediate layer together form the core, and (3) a cover being disposed about the core.
In one embodiment, the cover has at least one of a dimple coverage of greater than about 60 percent, a hardness from about 35 to 80 Shore D, or a flexural modulus of greater than about 500 psi, and wherein the golf ball has at least one of a compression from about 50 to 120 or a coefficient of restitution of greater than about 0.7. In another embodiment, the reaction product has a first dynamic stiffness measured at xe2x88x9250xc2x0 C. that is less than about 130 percent of a second dynamic stiffness measured at 0xc2x0 C.
Preferably, the cis-to-trans catalyst includes an organosulfur compound, an inorganic sulfide, a Group VIA component, or a combination thereof. In one preferred embodiment, the organosulfur compound is substantially free of metal and includes at least one of diphenyl disulfide or ditolyl disulfide, or both. In a more preferred embodiment, the organosulfur component includes ditolyl disulfide. The cis-to-trans catalyst is typically present in an amount from about 0.1 to 25 parts per hundred of polybutadiene. In a preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.1 to 12 parts per hundred of polybutadiene. In a more preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.1 to 8 parts per hundred of polybutadiene. In another embodiment, the cis-to-trans catalyst is present in an amount sufficient to produce the polybutadiene reaction product so as to contain at least about 32 percent trans-isomer. In another embodiment, the cis-to-trans catalyst further includes at least one of an aromatic organometallic compound, a metal-organosulfur compound, an aromatic organic compound, or a combination thereof.
When elemental sulfur or polymeric sulfur, or both, are included in a Group VIA component in the cis-to-trans catalyst, the reaction product can further include a vulcanization accelerator. In one embodiment, the vulcanization accelerator includes at least one of sulfenamide, thiazole, dithiocarbamate, thiuram, xanthate, thiadiazine, thiourea, guanadine, or aldchyde-amine. The accelerator, when used, is typically present in an amount from about 0.05 to 2 phr. In a preferred embodiment, the optional accelerator is present in an amount from about 0.1 to 1 phr.
In one embodiment, the polybutadiene reaction product includes less than about 7 percent vinyl-isomer content based on the total polybutadiene. In a preferred embodiment, the polybutadiene reaction product includes less than about 4 percent vinyl-isomer. In a more preferred embodiment, the polybutadiene reaction product includes less than about 2 percent vinyl-isomer.
The invention also includes a golf ball wherein the center including the material has a first point having a first hardness and a second point having a second hardness that is at least about 10 percent greater than the first hardness. In one embodiment, the golf ball center has a diameter from about 0.85 inches to 1.4 inches. In another embodiment, the core has a diameter from about 1.5 inches to 1.62 inches, while preferably the core has a diameter from about 1.51 inches to 1.6 inches.
The reaction product material formed from the conversion reaction typically has a first amount of trans-isomer at a first point in the center and a second amount of trans-isomer at a second point in the center, and wherein the first amount of trans-isomer is at least about 6 percent less than the second amount of trans-isomer. In one embodiment, the first amount of trans-isomer is at least about 10 percent less than the second amount of trans-isomer. In another additional or alternative embodiment, the second point has from about 35 percent to 60 percent of trans-isomer polybutadiene. In yet another such embodiment, the second point has from about 40 percent to 50 percent of trans-isomer polybutadiene.
The reinforcing polymer component in an intermediate layer is present in an amount of about 1 to 40 weight percent of the at least one intermediate layer and includes at least one of a block copolymer ether/ester, an acrylic polyol, a trans-polyisoprene, a transisomer polybutadiene, a 1,2-polybutadiene, an ethylene-vinyl acetate copolymer, a polyethylene or copolymer thereof, a trans-polycyclooctenamer, or a combination thereof. In one preferred embodiment, the reinforcing polymer component includes transpolyisoprene. In another preferred embodiment, the reinforcing polymer component includes a polybutadiene polymer with a trans-content greater than 90 percent and a vinyl content of less than 9 percent. In one preferred embodiment, the intermediate layer including the uncrosslinked first mixture has a rigidity as measured by a flexural modulus greater than about 7 MPa (xcx9c1,020 psi). All of the intermediate layers together typically have a total thickness of about 0.08 inches to 0.6 inches. In one embodiment, at least one intermediate layer includes a tensioned elastomeric material wound about the center. This tensioned elastomeric material can include the same or a different polybutadiene reaction product as the center.
The cover typically has a thickness of at least about 0.03 inches, preferably from about 0.03 to 0.125 inches, and can have a Shore D hardness of about 58 to 68. In one embodiment, the cover includes at least two layers.
In one preferred embodiment, the invention relates to a golf ball having: (1) a center including a reaction product material formed from the conversion reaction of sufficient amounts of polybutadiene, a free radical source, and a cis-to-trans catalyst to convert a portion of cis-isomer to trans-isomer in the polybutadiene, which reaction occurs at a sufficient temperature to form the material that contains trans-isomer and cis-isomer, wherein said material has an amount of trans-isomer greater than the amount of trans-isomer present before the conversion reaction, (2) at least one intermediate layer disposed about the center and including a resilient polymer component and a trans-polyisoprene component present in an amount of at least about 10 percent based on the total polymer content of the intermediate layer, and (3) a cover being disposed about the core. In another preferred embodiment, the trans-polyisoprene component is present in an amount of about 10 percent to 40 percent.
In another preferred embodiment, the invention relates to a golf ball having: (1) a center including a reaction product material formed from the conversion reaction of sufficient amounts of polybutadiene, a free radical source, and a cis-to-trans catalyst to convert a portion of cis-isomer to trans-isomer in the polybutadiene, which reaction occurs at a sufficient temperature to form the material that contains trans-isomer and cis-isomer, wherein said material has an amount of trans-isomer greater than the amount of trans-isomer present before the conversion reaction, (2) at least one intermediate layer disposed about the center and including a resilient polymer component and a trans-polybutadiene component present in an amount of at least about 15 percent based on the total polymer content of the intermediate layer, and (3) a cover being disposed about the core. In a preferred embodiment, the trans-polybutadiene component is present in an amount of about 15 percent to 40 percent.